Method for the preparation and handling of highly oxygen reactant materials

ABSTRACT

A method for the preparation and handling of predetermined quantity amounts of sodium or other highly oxygen reactant materials. The method comprises the steps of cutting a preselected length of the material from a source of the material disposed within protective plastic tubing of an indeterminate length and storing the precut lengths of tubing containing the material as a core in a container of liquid nitrogen. After suitable chilling in the liquid nitrogen the precut lengths of tubing are removed from the liquid nitrogen and the chilled core material is extruded from the plastic tubing and is reinserted into a liquid nitrogen bath for subsequent use as a predetermined quantity amount or dose of the material in handleable form.

United States Patent Fraser et a1.

[is] 3,656,826 [451 Apr. 18,1972

[72] Inventors: Hugh D. Fraser, West Caldwell; Leo C.

Werner, Cedar Grove, both of NJ.

1,835,118 12/1931 Marden et a1 ..75/66 X Westinghouse Electric Corporation, Pitt- I 3,094,442 6/1963 Perry ..148/125 X 3,185,600 5/1965 Dullberg.... 148/125 3,416,977 12/1968 Rein ..148/125 X Primary Examiner-John F. Campbell Assistant Examiner-Richard Bernard Lazarus Attorney-A. T. Stratton, W. D. Palmer and Blair R. Studebaker [5 7] ABSTRACT A method for the preparation and handling of predetermined quantity amounts of sodium or other highly oxygen reactant materials. The method comprises the steps of cutting a preselected length of the material from a source of the material disposed within protective plastic tubing of an indeterminate length and storing the precut lengths of tubing containing the material as a core in a container of liquid nitrogen. After suitable chilling in the liquid nitrogen the precut lengths of tubing are removed from the liquid nitrogen and the chilled core material is extruded from the plastic tubing and is reinserted into a liquid nitrogen bath for subsequent use as a predetermined quantity amount or close of the material in handleable form.

3 Claims, 1 Drawing Figure SEVER PREDETERMINED LENGTHS OF PLASTIC COATED SODIUM WIRE FROM A SOURCE IMMERSE PRE OF PLASTIC COATED SODIUM WIRE IN LIQUID NITROGEN CUT LENGTHS REMOVE PRE-CUT LENGTHS OF PLASTIC COATED SODIUM WIRE FROM LIQUID NITROGEN EXTRUDE SODIUM CORE IN FORM FROM PLASTIC COATING 0F PELLET IMMERSE EXTRUDED SODIUM PELLET IN LIQUID NITROGEN PATENTEIJIPII 18 I972 WITNESSES SEVER PREDETERMINED LENGTHS OF PLASTIC COATED SODIUM WIRE FROM A SOURCE IMMERSE PRE-CUT IENGTHS OF PLASTIC COATED SODIUM WIRE IN LIQUID NITROGEN REMOVE PRE-CUT LENGTHS OF PLASTIC COATED SODIUM WIRE FROM LIQUID NITROGEN EXTRUDE SODIUM CORE IN FORM OF PELLET FROM PLASTIC COATING IMMERSE EXTRUDED SODIUM PELLET IN LIQUID NITROGEN REMOVE SODIUM PELLET FROM LIQUID NITROGEN AND INSERT IN PREPARED CERAMIC ARC TUBE ATTORNEY METHOD FOR THE PREPARATION AND HANDLING OF HIGHLY OXYGEN REAC'IANT MATERIALS BACKGROUND OF THE INVENTION This invention relates to the preparation and handling of highly oxygen reactant materials and more particularly is directed to the preparation and handling of predetermined quantity amounts of sodium for use as one of the discharge sustaining constituents of a ceramic discharge lamp.

A significant factor in the manufacture of optimum quality ceramic discharge lamps is the ability to provide that lamp with a precise quantity of pure sodium. Efforts to provide a specific quantity of pure sodium for a discharge lamp have heretofore not been wholly successful due to the very nature of the sodium itself. At room temperature, in an oxygen atmosphere, sodium becomes sticky and, therefore, quite difficult to handle. In addition, because of oxidation of the exterior surface of the sodium pellet, efforts to achieve exact dosage amounts have been almost impossible.

A common method previously employed for preparing and handling precise dosage amounts of sodium has been through the use of a dry box containing an argon atmosphere. The dry box method is awkward, time-consuming and does not completely exclude oxidation of the sodium. Efforts to handle plastic sodium wire from which the sodium core is extruded have also not been successful because of the stickiness achieved by the exterior surface of the sodium at room temperature which will in a short period cause the operation of the dispensing apparatus to become impaired.

Dosing of ceramic discharge lamps by the dry box method permits about eight arc tubes to be dosed in a period of 60 minutes because of the necessity of many time-consuming steps, such as placing the materials into the box, pumping down the entrance chamber, transferring the materials to the dry box proper, weighing and preparing the materials, and finally removing the filled arc tubes from the dry box. The method of this invention will permit the same eight arc tubes to be dosed within about 5 minutes.

SUMMARY OF THE INVENTION This invention provides for the improved preparation and handling of exact predetermined quantity amounts of highly oxygen reactant materials. The method of this invention comprises the steps of severing a predetermined length of plastic coated oxygen reactant material from a source of such material of indeterminate length; storing the precut lengths of tubing in a container of liquid nitrogen, removing the precut length of tubing from the liquid nitrogen and extruding the chilled core of oxygen reactant material from the plastic outer tubing, reinserting the material into a liquid nitrogen bath in preparation for subsequent use as a predetermined quantity amount or dose of the material.

BRIEF DESCRIPTION OF THE DRAWINGS The method of the present invention will become more readily apparent and better understood as the following detailed description is considered in connection with the sole figure of the drawing which illustrates by block diagram the method of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The handling of highly oxygen reactant and moisture reactant materials has been a problem in the production of gas discharge lamps of the additive type for many years. With the arrival of the ceramic bodied discharge lamp the use of sodium, which when employed in a gas discharge lamp produces strong radiations near the middle of the visible spectrum or more particularly in that portion of the visible spectrum to which the eye is most sensitive, has become more realistically possible since the ceramic arc tube is not as susceptible to attack by the sodium as is the conventional quartz arc tube.

mosphere and tends to oxidize rapidly. In atmospheres containing a high moisture content even violent reactions can occur when pure sodium is contacted by such an atmosphere. It has, therefore, become necessary to device methods for getting sodium into the ceramic arc tube in substantially exact quantities which are untainted by oxidation.

One method for handling sodium for use in gas discharge lamps is disclosed in copending application Ser. No. 805,232, filed Mar. 7, 1969, now U.S. Pat. No. 3,584,359 patented June 15, 1971, entitled Method and Apparatus for Dispensing Measured Quantities of Highly Oxygen Reactant Materials, by Leo C. Werner et al. which application is owned by the assignee of the present application. Although the invention of the above described copending application represents a substantial advance in the handling of highly oxygen reactant materials, as, for example, sodium, in the dosing of ceramic discharge lamps, not all oxidation problems have been solved thereby.

As pointed out in said copending application, it is common practice to produce electrical conductors which include a pure sodium core coated or encased in a plastic tube. Pure sodium, which has been melted into a polyethylene tube for use as a certain kind of electrical conductor is available commercially from the Chemicals and Plastics Division of the Union Carbide Corporation. This sodium wire comprises a core of pure sodium surrounded by a polyethylene wall and is available in lengths up to 500 ft. and more. The wire includes a solid sodium core of either 60 or 80 mil. diameter each having a 30 mil. polyethylene wall of tubing thereabout.

Since the volume of sodium in the wire is uniform per unit of length, if a predetermined length of wire is cut off and the sodium core extruded from the polyethylene tubing, a slug or dose of sodium of a substantially exact quantity amount is obtainable and if oxidation of that slug or dose can be prevented, a substantially exact quantity of sodium can be dosed into the ceramic arc tube.

Freezing, or more specifically substantially lowering the temperature of the sodium reduces its chemical activity substantially and at lowered temperatures, sodium can be handled in an ambient atmosphere without significant oxidation or other chemical reaction.

The method of this invention contemplates providing exact quantity amounts of an uncontaminated highly oxygen reactant material, as for example sodium, by employing as a source of such sodium the above described plastic coated sodium wire. Since there is an exact relationship between the length of a sodium pellet taken from the plastic coated wire and its weight, if predetermined lengths of plastic coated sodium wire are severed from the source and maintained in an uncontaminated state until used, an exact amount of sodium will be dosed into the lamp. In accordance with this invention, after cutting, the plastic coated sodium wire is stored in precut lengths in a liquid nitrogen bath or container until a batch of ceramic arc tubes is ready to be closed. At this point in the process, the precut lengths of plastic coated sodium wire are removed from the liquid nitrogen and the chilled core of pure sodium in the form of a pellet or dose is extruded from the plastic coating and immediately immersed into a second bath of liquid nitrogen. The exact quantity sodium pellet is then removed from the second liquid nitrogen bath and inserted into the preexhausted, prebaked arc tube in preparation for the final sealing off of the arc tube body.

The sodium within the plastic tubing is, of course, protected from the ambient atmosphere by the plastic tubing; however, it will be apparent that the exposed end of the sodium core will oxidize. In practicing the method of this invention a small segment at the end of the wire can be cut ofi' and disposed of to insure the elimination of oxidized sodium which will build up on the end of the wire. Immediately thereafter plastic coated segments of predetermined lengths can be cut from the remaining portion of the wire and immediately disposed in the liquid nitrogen to prevent further oxidation of the ends. Extruding of the sodium core from the plastic coating is also Sodium is highly reactant with a conventional ambient atfacilitated by the freezing or chilling of the precut length of sodium wire since the sodium at these reduced temperatures will not become sticky and slides with relative ease from the external tubing. The liquid nitrogen renders the sodium sub stantially rock hard and renders the extrusion and handling processes quite simple as compared to the extruding and handling of unchilled or frozen sodium pellets, which tend to acquire a sticky coating, at room temperature.

As will be apparent from the foregoing, the method of handling highly oxygen reactive materials in accordance with this invention pennits the acquisition of exact quantity amounts unaffected by external oxidation. The foregoing is accomplished by severing predetermined lengths of plastic coated wire containing a core of the material, storing the precut lengths of coated material in the liquid nitrogen to reduce the temperature of the precut lengths; removing the precut lengths from the liquid nitrogen and extruding the core material from the plastic coating; immersing the material in the form of an extruded pellet in liquid nitrogen and removing the material from the second liquid nitrogen bath and inserting it into the pre-exhausted and prebaked arc tube.

We claim:

1. A method for the preparation and handling of highly oxygen reactant material comprising the steps of:

separating a predetermined quantity amount of said material from a source of said material;

storing said predetermined quantity amount of said material in a bath of liquid nitrogen to lower the temperature of said material substantially below ambient temperature; and

removing said predetermined quantity amount of said material from said liquid nitrogen and inserting said predetennined quantity amount of said material into a pre-exhausted and prebaked ceramic arc tube.

2. The method of preparing and handling a predetermined quantity amount of highly oxygen reactant material according to claim 1 wherein said highly oxygen reactant material is sodium.

3. A method for the preparation and handling of predetermined quantity amounts of sodium for use .in ceramic discharge lamps comprising the steps of:

cutting a predetermined length from a source of plastic coated pure sodium wire of indetenninate length; storing the precut lengths of plastic coated sodium in liquid nitrogen;

removing the precut lengths of plastic coated sodium from the liquid nitrogen and extruding an exact amount of sodium core in the form of a pellet from the plastic coating;

immersing the extruded sodium pellet in liquid nitrogen;

and removing the sodium pellet from the liquid nitrogen and inserting said pellet into a pre-exhausted and prebaked ceramic arc tube. 

2. The method of preparing and handling a predetermined quantity amount of highly oxygen reactant material according to claim 1 wherein said highly oxygen reactant material is sodium.
 3. A method for the preparation and handling of predetermined quantity amounts of sodium for use in ceramic discharge lamps comprising the steps of: cutting a predetermined length from a source of plastic coated pure sodium wire of indeterminate length; storing the precut lengths of plastic coated sodium in liquid nitrogen; removing the precut lengths of plastic coated sodium from the liquid nitrogen and extruding an exact amount of sodium core in the form of a pellet from the plastic coating; immersing the extruded sodium pellet in liquid nitrogen; and removing the sodium pellet from the liquid nitrogen and inserting said pellet into a pre-exhausted and prebaked ceramic arc tube. 